Elements Spine SRS from Brainlab
Started by SBRTreble
We just bought it and are working on commissioning it on our machine. We've been using brainlab multimet cranial module and it's great. I had a long discussion about elements with our physicist. One of the biggest issues we've had planning spine SBRT with pinnacle is the plans frequently fail QA and we have to replan. Pinnacle tries to come up with complicated plans to create the needed steep gradients, which leads to a relatively high failure rate. Elements is solely designed for spine SBRT and gives you elegant solutions that're more practical and deliverable. Having said that, we haven't used it on a real patient yet. But as I said, their cranial plans are amazing and easily deliverable, so I have no reason to doubt their spine module
We’re looking to get this along with the functional platform that helps with contouring out some of those pathways. Have to say, I’m sold on the products.
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deleted1116990
How do you all approach spine SBRT adjacent to a previously treated level?
Patient previously got 24/2 to T5 (vetebral body only) 6 months ago. Now has hypermetabolic lesion in vertebral body of T4. Reasonable to SBRT the FDG-avid area and not treat the rest of the body? Or would you treat the whole body but pull off cord inferiorly?
Continuing to monitor risks progression and having to treat a larger area potentially retreating cord.
Not treating the whole body risks marginal failure or local recurrence and trying to patch that area up a 3rd time, again overexposing cord.
Patient previously got 24/2 to T5 (vetebral body only) 6 months ago. Now has hypermetabolic lesion in vertebral body of T4. Reasonable to SBRT the FDG-avid area and not treat the rest of the body? Or would you treat the whole body but pull off cord inferiorly?
Continuing to monitor risks progression and having to treat a larger area potentially retreating cord.
Not treating the whole body risks marginal failure or local recurrence and trying to patch that area up a 3rd time, again overexposing cord.
Cop-out answer: treat as much of T4 as possible to keep yourself comfortable, treat as little of T4 as possible to keep the DVH for cord reasonable, and treat the hypermetabolic lesion.
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deleted1116990
Thanks, I'll probably do this and just be very conservative near the posterior edge of the VB. Thankfully the lesion is central.
This is a stupid question, and I am going to expose some gaps in my knowledge/training, but what is the data behind the consensus guidelines for treating the whole vertebral body or for instance, transverse process or posterior elements in some cases rather than just the lesion on MRI/PET + PTV margin? Presumably the thought is the rest of the bone harbors micrometastatic disease. We don't do this in other bones, just spine. Why? Patterns of failure analysis?
Excellent question, I've asked myself the same often.
What we have done in our clinic was to use different dose levels.
We treat the entire vertebral body with one dose level and SIB to what we see on CT/MRI/PET with another dose.
Dose to the entire vertrebral body is generally below spinal cord constraints, dose to lesion is then higher.
For instance 6 x 4 Gy to vertebral body and 6 x 6 Gy to the lesion (GTV + 3mm CTV-margin).
Add to that a PTV margin, depending on how comfortable you are with your immobilization.
As far as I know. those guidelines are not evidence based but simply a consensus of the people who were involved (and if you look at the pre-consensus volumes they are all over the place). There are patterns of failure studies that probably impacted how the experts drew their volumes.
pubmed.ncbi.nlm.nih.gov
pubmed.ncbi.nlm.nih.gov
pubmed.ncbi.nlm.nih.gov
Phase I/II study of stereotactic body radiotherapy for spinal metastasis and its pattern of failure - PubMed
Analysis of the data obtained in the present study supports the safety and effectiveness of SBRT in cases of spinal metastatic cancer. The authors consider it prudent to routinely treat the pedicles and posterior elements using a wide bone margin posterior to the diseased vertebrae because of...
pubmed.ncbi.nlm.nih.gov
Patterns of failure after single-dose radiosurgery for spinal metastasis - PubMed
Spine-related pain control/reduction was excellent. Tumor recurrence at the treated segment and progression to the immediately adjacent region were rare. The results support the use of spinal radiosurgery as an effective treatment option for solitary spinal metastasis.
pubmed.ncbi.nlm.nih.gov
Marginal recurrence requiring salvage radiotherapy after stereotactic body radiotherapy for spinal metastases - PubMed
SBRT for spinal metastases results in a low overall rate of MR. The presence of paraspinal disease at the time of SBRT and a dose of <16 Gy were associated with higher risks of MR.
pubmed.ncbi.nlm.nih.gov
Cancer cells in vertebral bones are capable of subclinical spread within the vertebral body. Cancer cells don’t subclinically spread in non-vertebral bones. I’m very surprised you didn’t know that!
Made up. Have moved to just treating gross disease with a small PTV margin.
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deleted1116990
So we've been taking the cord to tolerance for no proven reason? Hmmmm... Wonder if you would fail boards for saying this.
Same folks who said it we had to treat level above and below. Can't shake history.
Depends on if examiner is a guideline author
IOW what we do for every other oligomet
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deleted1116990
Thank you all. I feel less stupid/crazy. Amazing when you think about it that this was never discussed in 4 years of residency.
They are even able to infiltrate through intervertebral discs and beyond. That's why:
"One above and one below"!
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deleted1116990
The argument I was told was that you needed to cover above and below to prevent a failure and have to come back and treat next to a previously treated level. Well what if it fails above and below that? And where do you set your block? If the 95% isodose line covers the top of the VB + PTV margin extending into the next level, there is going to be significant dose to half of the adjacent level. The whole thing seemed ridiuclous.
So I have to ask you guys. What part of the spine is most commonly involved with metastases and why. Cervical, thoracic, lumbar, or sacral?
Also helped prevent misses for those boomers with trouble identifying vertebral body numbers...
I think that’s exactly why they used to do that
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deleted1116990
Sacrum. Gravity? I'm going to go with gravity.
Nope but good logic
It’s thoracic … because bony mets tend to distribute randomly, and we have more thoracic vertebrae so it’s a probabilistic thing (or so I’ve been told)
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deleted1116990
Haha I was joking as that made about as much sense as above and below. I assumed it was a volume thing as well.
Relevant study:
pubmed.ncbi.nlm.nih.gov
I stick to the guidelines.
Deviation from consensus contouring guidelines predicts inferior local control after spine stereotactic body radiotherapy - PubMed
Adherence to consensus contouring guidelines for spine SBRT is associated with superior LC and fewer marginal misses.
pubmed.ncbi.nlm.nih.gov
I stick to the guidelines.
Thanks for this. Always good to re-examine assumptions. Not sure I buy it as identified a few weaknesses in the analysis on cursory review but food for thought.Relevant study:
Deviation from consensus contouring guidelines predicts inferior local control after spine stereotactic body radiotherapy - PubMed
Adherence to consensus contouring guidelines for spine SBRT is associated with superior LC and fewer marginal misses.
I stick to the guidelines.
There was a recent paper reviewed on quadshot but i cant seem to find it. Basically they looked at a large series of SBRT cases which were concordant with “guidelines”
And i believe there was a cohort which did not follow them. Guideline cohort had less recurrences. A lot of recurrences were in areas that should have been covered per “guidelines”. In the end, it is expert opinion, but this does not make it wrong. If anybody remembers what im referencing please link?
Well you know "drop" is what a thing does in the presence of a gravitational field right?
Drop metastases are real, and Krukenberg tumors may be "drop mets" too.
Agree with you and do something similar except I do 5 treatments cuz, you know, thats the only real sbrt. Our whole of residency it is pounded into us that subclinical disease requires a lower dose than gross disease, yet somehow the spine is different?
Treat the entire vertebral body and dose paint at the inferior edge to avoid overdosing cord.
Treating one above and one below w/ 3D helps to avoid splitting a vertebral body in half with radiation while getting 95/95-100 coverage to the entire vertebral body that is actually at risk.
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